topic Plot variables over a common X-Axis in Mathcad

Plot variables over a common X-Axis

thodij — Sat, 28 Feb 2026 16:14:45 GMT

Hi PTC Community -

I have two variable quantities (Water & Ammonia) evaluated over two different temperature ranges over which only they are each valid.

I would like to plot both with a common x-axis range (-70°C to +370°C), and not be limited to either the T1 or T2 (MIN, MAX) range.

See how the Ammonia (pink) plot is being limited to the MIN(T1) value of 1°C.

See attached. I am using Mathcad Prime 11.0.1.0.

Your tips and suggestions for a fix will be appreciated.

Regards,

thodij

Re: Plot variables over a common X-Axis

LucMeekes — Sat, 28 Feb 2026 16:37:11 GMT

Add a second ordinate expression, match the order up such that you have the right T(2?) to go with the ammonia and then T(1?) with water.

Success!
Luc

Re: Plot variables over a common X-Axis

thodij — Sat, 28 Feb 2026 16:50:11 GMT

Luc,

Thank you for your response.

I do not see how to do that from the plots menu.

Thanks,

thodij

Re: Plot variables over a common X-Axis

Werner_E — Sat, 28 Feb 2026 18:43:01 GMT

Like this?

You can add expressions at the abscissa the same way as you did at the ordinate - either via the menu using "add trace" or by the keyboard short Ctrl+Enter

Re: Plot variables over a common X-Axis

LucMeekes — Sat, 28 Feb 2026 18:48:02 GMT

Put your cursor on the T1 (X-axis variable) and select "Add trace" from the Plots menu.

Now the order of X-axis expressions must match what is needed for the corresponding Y-axis expression. If there are less X-axis expressions then Y-axis expressions, the last X-axis expression is used for every subsequent Y-axis expression. That is what you had (1 X-axis expression for the first, and the second Y-axis expression).
In the mean time, Werner has shown what it looks like.

It's as simple, and intuitive as every other interface of Prime.

Success!
Luc

Re: Plot variables over a common X-Axis

thodij — Sat, 28 Feb 2026 19:42:40 GMT

Perfect!

This is what I am looking for.

Thanks to Werner, and Luc.

Regards,

thodij